Perfluoroalkyloxetanes



United Statcs Patent 3,096,344 PERFLUOROALKYLOXETANES Leslie C. Case, Lafayette, Ind., assignor to Research Corporation, New York, N.Y., a corporation of New York No Drawing. Filed May 9, 1961, Ser. No. 108,720 3 Claims. (Cl. 260-333) This invention relates to novel polyfluoroalkyloxetanes.

It has been found that oxetanes having at least one polyfluor-inated alkyl group attached to a ring carbon atom may be converted by polymerization or copolymerization to polymeric substances which can be converted by reaction with curing or cross-linking reactants to elastomeric products of high heat stability useful as temperature resistant elastomers and as flexible temperature resistant films and coatings. The monomeric oxetanes of the invention are also useful for producing a wide variety of compounds containing .polyfiuoroalkyl groups by reacting the oxetanes with compounds containing active hydrogens, such as alcohols, amines and the like.

Of particular usefulness are oxet-anes containing at least one polyfiuoroalkyl group containing from two to eleven carbon atoms attached to the 3-carbon atom of the oxetane ring.

A method of general applicability for producing oxetanes of the invention having polyfluoroalkyl groups containing from two to ten carbon atoms attached to the 3- carbon atom of the oxetane ring comprises acylating malonic or alkylmalonic esters with polyiluoroalkanoyl halides to produce the corresponding polyfluoroalleanoylmalonic esters, reacting the malonic esters thus obtained with sulfur tetrafluoride to substitute two fluorines for the carbonyl oxygen of the polyfluoroalkanoyl group and reducing the polyfluoroalkylmalonic ester thus obtained to the corresponding 2-polyfluoroalkyl-1,3-propanediol with LiAlH The propanediol is then converted to the corresponding 3-polyfluoroalkyloxetane by the method of U.S. patent application Serial No. 835,835, now Patent 3,006,926, for Production of Cyclic Ethers, filed August 25, 1959, by Leslie C. Case and Laurence F. Schmoyer.

When starting with unsubstituted malonic esters in the method outlined above either one or both of the hydro gens in the 2-position of the ester may be replaced by polyfluoroalkanoyl groups.

Among the polyfluoroalkanoic acids which may be used in the method are:

CF .COOH. CF .(CF ),,.COOH, where in n is 1 to 8.

Other polyfiuoroalkanoic acids are listed in Table 20, pages 210-215 of Aliphatic Fluorine Compounds, by Lovelace, Postelnek and Rausch (New York, 1958).

Oxetanes substituted in the 2-position may be made from the aldehydes of the polyfluoroalkanoic acids discussed above. The aldehydes may be obtained by reduction of the acids or their esters with LiAlH The polyfiuoroalk-anal is reacted with a haloacetic acid ester and zinc in the Reformatsky reaction to give the corresponding 3-polyfluoroalkyl-3-hydroxypropionic ester, which is reduced to the 1,3-diol with LiAlH The diol is condensed to the Z-polyfluoroalkyl oxetane by the method of the Case and Schmoyer application referred to above.

A method particularly suitable for the production of the 3,3-di(trifluoromethyl)oxetane comprises condensing diethyl malonate with formaldehyde under alkaline conditions to give the diethyl ester of di(hydroxymethyl) malonic acid, este-rifying the hydroxyl groups with a blocking acid such as benzoic acid, converting the -COOC H groups of the malonic ester to CF groups by direct action of SF, or by preferential hydrolysis to the malonic acid followed by fiuorination with SP The blocking 3,098,344 Patented July 2, 1963 2 acid groups are then hydrolized off, giving the 2,2-di(-trifluoromethyl)-1,3 propanediol which is converted to 3,3- di(trifluoromethyl)oxetane by the method of the Case and Schmoyer application.

The following are illustrative specific examples of methods of making the new polyfluoroalkyloxetanes of the invention.

10 gm. of sodium are dissolved in 300 ml. of absolute ethanol in a 500 ml. flask. 81.2 gm. of diethyl ethy1- malonate are added and the solution is evaporated under vacuum until a dry solid salt is obtained. The salt is dissolved in the flask in 200 ml. of dry diethyl carbonate and gm. of heptafluorobutyryl chloride are dropped slowly into the solution at room temperature. The reaction mixture is then refluxed with stirring for about 40 hours and cooled. The liquid is decanted from the solid precipitate and the latter is dissolved in water, extracted with ether and the extract added to the decanted liquid. After removal of the volatile solvent under vacuum, the residual diethyl ethyl-heptafiuorobutrylmalonate is vacuum distilled. B.P 106-1l4 C. (12 mm. Hg), 11 1.3818, d: 1.2588.

75 gm. of the ethyl-heptafluorobutyrylrnalonic ester in 200 ml. of benzene are placed in a 500 ml. stainless steel autoclave and 29 gm. of SR, are charged into the autoclave. The mixture is heated at 150 C. for 8 hours with agitation. The reaction mixture is treated with NaF in ether solution to react with any HF and the solution is filtered and vacuum distilled. The diethyl ethylnonafluorobutylmalonate thus obtained boils at l13.5 C. (11 mm. Hg), 11 1.3801, d: 1.2937.

14 gm. of LiAlH, are dissolved in 250 ml. of dry ether and 50 gm. of the ethyl-nonafluorobutylmalonic ester dissolved in twice its volume of ether is slowly dropped into the LiAlH, solution. The mixture is stirred over night and after destroying excess LiAlH with water-saturated ether, cold sulfuric acid (40 m1. of 96% H SO and 200' gm. of ice) is slowly added. The acid layer is separated from the organic layer and extracted with 50 n11. of ether and 3 portions of benzene totaling 250 ml. The cornbined extracts and organic layer are vacuum distilled. .The 2-e-thyl-2-nonafluorobutyl-l,3propanedio1 boils at 146 C.150 C. (11 mm. Hg), n 1.4029.

1.5 gm. of the propanediol thus obtained are dissolved in 2.5 ml. of 96% H 80, and dropped slowly into a boiling solution of gm. of NaOH in 53.5 ml. of water in a flask equipped with stirrer, dropping funnel, condenser and ice-cooled receiver. The distillate comes over at a vapor temperature between 70-100 C. The 2-ethyl-2- nonafiuorobuty-loxctane is extracted from the distillate with ether and the extract is fractionated at atmospheric pressure. B.P. 140.5 C., n 1.3789.

Z-Heptayluoropropyloxetane In a 1-liter flask equipped with a reflux condenser and a magnetic stirrer are placed 100 ml. of dry ether, 100 ml. of dry benzene, 64 gm. of heptafluorobutyraldehyde, 53.4 gm. of ethylbromoacetate and 22.9 gm. of zinc dust. After 2 hours of refluxing 4 gm. of dust are added and refluxing is continued for 7 more hours. The reaction mixture is then poured into a cold acid solution made by pouring 40 ml. of 96% sulfuric acid over 400 gm. of ice. The organic layer is separated from the aqueous layer, the latter is extracted with three 100 ml. portions of ether and the ether extracts are added to the organic layer. The mixture is washed with ml. of saturated NaHCO solution and 150 ml. of water and dried over anhydrous calcium sulfate. After evaporating the bulk of the ether and benzene at atmospheric pressure, the ethyl 6,6,6,5,5,4,4-heptafluoro-3-hydroxyhexanoate is dis- 3 tilled under vacuum. B.P. 80-95 C. (9 mm. Hg), n 1.3539.

52.7 gm. of the ester thus obtained is dissolved in an equal volume of dry ether and dropped slowly into a solution of 14 gm. of LiA1H in 250 of dry ether. The mixture is stirred over night, and excess LiAlH is then destroyed with 400 ml. of water-saturated ether. A cold acid solution from 50 ml. of 96% H 80 and 250 gm. of ice is added cautiously to the reaction mixture. The ether layer is separated, the aqueous layer is extracted with 100 ml. of ether and three portions of benzene totaling 250 ml., and the extracts are added to the ether layer. After evaporating off the ether at atmospheric pressure, the residual benzene solution is cooled and white solid crystals of 6,6,6,5,5,4,4-heptafluoro-1,3-hexanediol which separate are filtered ofi. M.P. 9192 C.

41.0 gm. of the diol thus obtained are dissolved in 9.3 ml. of 96% H 80 and dropped slowly into a boiling solution of 240 gm. of NaOH in 107 ml. of water in a flask equipped with stirrer, condenser and dropping funnel. The 2-heptafiuoropropyloxetane formed .distills oil with water at a vapor temperature of between 70 C. and 90 C. The distillate is "collected in an ice-cooled flask. The organic layer is separated and dried over anhydrous calcium sulfate. B.P. 105-107 0., 11 1.3146.

The polyfiuorooxetanes oi the invention can be polymerized in solvents, such as methylene chloride and liquid sulfur dioxide or without solvents, 'by means of condensation catalysts, such as hydrogen fluoride, B1 and BF molecular complexes, for example, with acetonitrile, acetic acid and ether.

The polymerized polyfluorooxetanes can be cured to heat resistant elastomeric products by reacting with polyisocyanates such as tolylene diisocyanate and thereafter with compounds containing a plurality of reactive hydrogens such as 4,4adiaminodiphenylmethane, or by reacting with a free radical generator and a free radical acceptor using the reagents and procedures described in US. Patent 2,906,738 to Earl I. Goldberg.

'Copoly-merizates of the polyfluorooxetanes with oxetane, alkyloxetanes, and tetrahydrofurane can also be cross-linked by the foregoing methods.

'Copolymerization of the polyfluorooxetanes with chloroalkylethylene oxides, such as chloromethylethylene oxides provide chlorine containing copolymers which can be cross-linked with diamines or by the action of zinc oxide.

ugh

H 0 Ha OER:

wherein R is a perfluoro lower alkyl group of 1 to 9 carbon atoms.

2. An oxetane of the formula 0 R1 R2 wherein R is a perfluoro lower alkyl group of 1 to 9 carbon atoms and R is lower alkyl of 1 to 2 carbon atoms.

3. An oxetane of the formula R1 H wherein R is a perfiuoro lower alkyl group of 1 to 9 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS Harris Aug. 8, 1961 Harris Aug. 8, 1961 OTHER REFERENCES 

1. AN OXETANE SELECTED FROM THE GROUP CONSISTING OF OXETANES OF THE FORMULA 